Class AbstractQueuedLongSynchronizer
- java.lang.Object
-
- java.util.concurrent.locks.AbstractOwnableSynchronizer
-
- java.util.concurrent.locks.AbstractQueuedLongSynchronizer
- All Implemented Interfaces:
Serializable
public abstract class AbstractQueuedLongSynchronizer extends AbstractOwnableSynchronizer implements Serializable
A version of AbstractQueuedSynchronizer
in which synchronization state is maintained as a long
. This class has exactly the same structure, properties, and methods as AbstractQueuedSynchronizer
with the exception that all state-related parameters and results are defined as long
rather than int
. This class may be useful when creating synchronizers such as multilevel locks and barriers that require 64 bits of state.
See AbstractQueuedSynchronizer
for usage notes and examples.
- Since:
- 1.6
- See Also:
- Serialized Form
Nested Class Summary
Modifier and Type | Class | Description |
---|---|---|
class | AbstractQueuedLongSynchronizer.ConditionObject | Condition implementation for a |
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | AbstractQueuedLongSynchronizer() | Creates a new |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | acquire(long arg) | Acquires in exclusive mode, ignoring interrupts. |
void | acquireInterruptibly(long arg) | Acquires in exclusive mode, aborting if interrupted. |
void | acquireShared(long arg) | Acquires in shared mode, ignoring interrupts. |
void | acquireSharedInterruptibly(long arg) | Acquires in shared mode, aborting if interrupted. |
protected boolean | compareAndSetState(long expect,
long update) | Atomically sets synchronization state to the given updated value if the current state value equals the expected value. |
Collection<Thread> | getExclusiveQueuedThreads() | Returns a collection containing threads that may be waiting to acquire in exclusive mode. |
Thread | getFirstQueuedThread() | Returns the first (longest-waiting) thread in the queue, or |
Collection<Thread> | getQueuedThreads() | Returns a collection containing threads that may be waiting to acquire. |
int | getQueueLength() | Returns an estimate of the number of threads waiting to acquire. |
Collection<Thread> | getSharedQueuedThreads() | Returns a collection containing threads that may be waiting to acquire in shared mode. |
protected long | getState() | Returns the current value of synchronization state. |
Collection<Thread> | getWaitingThreads(AbstractQueuedLongSynchronizer.ConditionObject condition) | Returns a collection containing those threads that may be waiting on the given condition associated with this synchronizer. |
int | getWaitQueueLength(AbstractQueuedLongSynchronizer.ConditionObject condition) | Returns an estimate of the number of threads waiting on the given condition associated with this synchronizer. |
boolean | hasContended() | Queries whether any threads have ever contended to acquire this synchronizer; that is, if an acquire method has ever blocked. |
boolean | hasQueuedPredecessors() | Queries whether any threads have been waiting to acquire longer than the current thread. |
boolean | hasQueuedThreads() | Queries whether any threads are waiting to acquire. |
boolean | hasWaiters(AbstractQueuedLongSynchronizer.ConditionObject condition) | Queries whether any threads are waiting on the given condition associated with this synchronizer. |
protected boolean | isHeldExclusively() | Returns |
boolean | isQueued(Thread thread) | Returns true if the given thread is currently queued. |
boolean | owns(AbstractQueuedLongSynchronizer.ConditionObject condition) | Queries whether the given ConditionObject uses this synchronizer as its lock. |
boolean | release(long arg) | Releases in exclusive mode. |
boolean | releaseShared(long arg) | Releases in shared mode. |
protected void | setState(long newState) | Sets the value of synchronization state. |
String | toString() | Returns a string identifying this synchronizer, as well as its state. |
protected boolean | tryAcquire(long arg) | Attempts to acquire in exclusive mode. |
boolean | tryAcquireNanos(long arg,
long nanosTimeout) | Attempts to acquire in exclusive mode, aborting if interrupted, and failing if the given timeout elapses. |
protected long | tryAcquireShared(long arg) | Attempts to acquire in shared mode. |
boolean | tryAcquireSharedNanos(long arg,
long nanosTimeout) | Attempts to acquire in shared mode, aborting if interrupted, and failing if the given timeout elapses. |
protected boolean | tryRelease(long arg) | Attempts to set the state to reflect a release in exclusive mode. |
protected boolean | tryReleaseShared(long arg) | Attempts to set the state to reflect a release in shared mode. |
Methods declared in class java.util.concurrent.locks.AbstractOwnableSynchronizer
getExclusiveOwnerThread, setExclusiveOwnerThread
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Constructor Detail
AbstractQueuedLongSynchronizer
protected AbstractQueuedLongSynchronizer()
Creates a new AbstractQueuedLongSynchronizer
instance with initial synchronization state of zero.
Method Detail
getState
protected final long getState()
Returns the current value of synchronization state. This operation has memory semantics of a volatile
read.
- Returns:
- current state value
setState
protected final void setState(long newState)
Sets the value of synchronization state. This operation has memory semantics of a volatile
write.
- Parameters:
-
newState
- the new state value
compareAndSetState
protected final boolean compareAndSetState(long expect, long update)
Atomically sets synchronization state to the given updated value if the current state value equals the expected value. This operation has memory semantics of a volatile
read and write.
- Parameters:
-
expect
- the expected value -
update
- the new value - Returns:
-
true
if successful. False return indicates that the actual value was not equal to the expected value.
tryAcquire
protected boolean tryAcquire(long arg)
Attempts to acquire in exclusive mode. This method should query if the state of the object permits it to be acquired in the exclusive mode, and if so to acquire it.
This method is always invoked by the thread performing acquire. If this method reports failure, the acquire method may queue the thread, if it is not already queued, until it is signalled by a release from some other thread. This can be used to implement method Lock.tryLock()
.
The default implementation throws UnsupportedOperationException
.
- Parameters:
-
arg
- the acquire argument. This value is always the one passed to an acquire method, or is the value saved on entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like. - Returns:
-
true
if successful. Upon success, this object has been acquired. - Throws:
-
IllegalMonitorStateException
- if acquiring would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly. -
UnsupportedOperationException
- if exclusive mode is not supported
tryRelease
protected boolean tryRelease(long arg)
Attempts to set the state to reflect a release in exclusive mode.
This method is always invoked by the thread performing release.
The default implementation throws UnsupportedOperationException
.
- Parameters:
-
arg
- the release argument. This value is always the one passed to a release method, or the current state value upon entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like. - Returns:
-
true
if this object is now in a fully released state, so that any waiting threads may attempt to acquire; andfalse
otherwise. - Throws:
-
IllegalMonitorStateException
- if releasing would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly. -
UnsupportedOperationException
- if exclusive mode is not supported
tryAcquireShared
protected long tryAcquireShared(long arg)
Attempts to acquire in shared mode. This method should query if the state of the object permits it to be acquired in the shared mode, and if so to acquire it.
This method is always invoked by the thread performing acquire. If this method reports failure, the acquire method may queue the thread, if it is not already queued, until it is signalled by a release from some other thread.
The default implementation throws UnsupportedOperationException
.
- Parameters:
-
arg
- the acquire argument. This value is always the one passed to an acquire method, or is the value saved on entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like. - Returns:
- a negative value on failure; zero if acquisition in shared mode succeeded but no subsequent shared-mode acquire can succeed; and a positive value if acquisition in shared mode succeeded and subsequent shared-mode acquires might also succeed, in which case a subsequent waiting thread must check availability. (Support for three different return values enables this method to be used in contexts where acquires only sometimes act exclusively.) Upon success, this object has been acquired.
- Throws:
-
IllegalMonitorStateException
- if acquiring would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly. -
UnsupportedOperationException
- if shared mode is not supported
tryReleaseShared
protected boolean tryReleaseShared(long arg)
Attempts to set the state to reflect a release in shared mode.
This method is always invoked by the thread performing release.
The default implementation throws UnsupportedOperationException
.
- Parameters:
-
arg
- the release argument. This value is always the one passed to a release method, or the current state value upon entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like. - Returns:
-
true
if this release of shared mode may permit a waiting acquire (shared or exclusive) to succeed; andfalse
otherwise - Throws:
-
IllegalMonitorStateException
- if releasing would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly. -
UnsupportedOperationException
- if shared mode is not supported
isHeldExclusively
protected boolean isHeldExclusively()
Returns true
if synchronization is held exclusively with respect to the current (calling) thread. This method is invoked upon each call to a AbstractQueuedLongSynchronizer.ConditionObject
method.
The default implementation throws UnsupportedOperationException
. This method is invoked internally only within AbstractQueuedLongSynchronizer.ConditionObject
methods, so need not be defined if conditions are not used.
- Returns:
-
true
if synchronization is held exclusively;false
otherwise - Throws:
-
UnsupportedOperationException
- if conditions are not supported
acquire
public final void acquire(long arg)
Acquires in exclusive mode, ignoring interrupts. Implemented by invoking at least once tryAcquire(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success. This method can be used to implement method Lock.lock()
.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquire(long)
but is otherwise uninterpreted and can represent anything you like.
acquireInterruptibly
public final void acquireInterruptibly(long arg) throws InterruptedException
Acquires in exclusive mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once tryAcquire(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success or the thread is interrupted. This method can be used to implement method Lock.lockInterruptibly()
.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquire(long)
but is otherwise uninterpreted and can represent anything you like. - Throws:
-
InterruptedException
- if the current thread is interrupted
tryAcquireNanos
public final boolean tryAcquireNanos(long arg, long nanosTimeout) throws InterruptedException
Attempts to acquire in exclusive mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once tryAcquire(long)
, returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success or the thread is interrupted or the timeout elapses. This method can be used to implement method Lock.tryLock(long, TimeUnit)
.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquire(long)
but is otherwise uninterpreted and can represent anything you like. -
nanosTimeout
- the maximum number of nanoseconds to wait - Returns:
-
true
if acquired;false
if timed out - Throws:
-
InterruptedException
- if the current thread is interrupted
release
public final boolean release(long arg)
Releases in exclusive mode. Implemented by unblocking one or more threads if tryRelease(long)
returns true. This method can be used to implement method Lock.unlock()
.
- Parameters:
-
arg
- the release argument. This value is conveyed totryRelease(long)
but is otherwise uninterpreted and can represent anything you like. - Returns:
- the value returned from
tryRelease(long)
acquireShared
public final void acquireShared(long arg)
Acquires in shared mode, ignoring interrupts. Implemented by first invoking at least once tryAcquireShared(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared(long)
until success.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquireShared(long)
but is otherwise uninterpreted and can represent anything you like.
acquireSharedInterruptibly
public final void acquireSharedInterruptibly(long arg) throws InterruptedException
Acquires in shared mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once tryAcquireShared(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared(long)
until success or the thread is interrupted.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquireShared(long)
but is otherwise uninterpreted and can represent anything you like. - Throws:
-
InterruptedException
- if the current thread is interrupted
tryAcquireSharedNanos
public final boolean tryAcquireSharedNanos(long arg, long nanosTimeout) throws InterruptedException
Attempts to acquire in shared mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once tryAcquireShared(long)
, returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared(long)
until success or the thread is interrupted or the timeout elapses.
- Parameters:
-
arg
- the acquire argument. This value is conveyed totryAcquireShared(long)
but is otherwise uninterpreted and can represent anything you like. -
nanosTimeout
- the maximum number of nanoseconds to wait - Returns:
-
true
if acquired;false
if timed out - Throws:
-
InterruptedException
- if the current thread is interrupted
releaseShared
public final boolean releaseShared(long arg)
Releases in shared mode. Implemented by unblocking one or more threads if tryReleaseShared(long)
returns true.
- Parameters:
-
arg
- the release argument. This value is conveyed totryReleaseShared(long)
but is otherwise uninterpreted and can represent anything you like. - Returns:
- the value returned from
tryReleaseShared(long)
hasQueuedThreads
public final boolean hasQueuedThreads()
Queries whether any threads are waiting to acquire. Note that because cancellations due to interrupts and timeouts may occur at any time, a true
return does not guarantee that any other thread will ever acquire.
- Returns:
-
true
if there may be other threads waiting to acquire
hasContended
public final boolean hasContended()
Queries whether any threads have ever contended to acquire this synchronizer; that is, if an acquire method has ever blocked.
In this implementation, this operation returns in constant time.
- Returns:
-
true
if there has ever been contention
getFirstQueuedThread
public final Thread getFirstQueuedThread()
Returns the first (longest-waiting) thread in the queue, or null
if no threads are currently queued.
In this implementation, this operation normally returns in constant time, but may iterate upon contention if other threads are concurrently modifying the queue.
- Returns:
- the first (longest-waiting) thread in the queue, or
null
if no threads are currently queued
isQueued
public final boolean isQueued(Thread thread)
Returns true if the given thread is currently queued.
This implementation traverses the queue to determine presence of the given thread.
- Parameters:
-
thread
- the thread - Returns:
-
true
if the given thread is on the queue - Throws:
-
NullPointerException
- if the thread is null
hasQueuedPredecessors
public final boolean hasQueuedPredecessors()
Queries whether any threads have been waiting to acquire longer than the current thread.
An invocation of this method is equivalent to (but may be more efficient than):
getFirstQueuedThread() != Thread.currentThread() && hasQueuedThreads()
Note that because cancellations due to interrupts and timeouts may occur at any time, a true
return does not guarantee that some other thread will acquire before the current thread. Likewise, it is possible for another thread to win a race to enqueue after this method has returned false
, due to the queue being empty.
This method is designed to be used by a fair synchronizer to avoid barging. Such a synchronizer's tryAcquire(long)
method should return false
, and its tryAcquireShared(long)
method should return a negative value, if this method returns true
(unless this is a reentrant acquire). For example, the
tryAcquire
method for a fair, reentrant, exclusive mode synchronizer might look like this:
protected boolean tryAcquire(int arg) { if (isHeldExclusively()) { // A reentrant acquire; increment hold count return true; } else if (hasQueuedPredecessors()) { return false; } else { // try to acquire normally } }
- Returns:
-
true
if there is a queued thread preceding the current thread, andfalse
if the current thread is at the head of the queue or the queue is empty - Since:
- 1.7
getQueueLength
public final int getQueueLength()
Returns an estimate of the number of threads waiting to acquire. The value is only an estimate because the number of threads may change dynamically while this method traverses internal data structures. This method is designed for use in monitoring system state, not for synchronization control.
- Returns:
- the estimated number of threads waiting to acquire
getQueuedThreads
public final Collection<Thread> getQueuedThreads()
Returns a collection containing threads that may be waiting to acquire. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order. This method is designed to facilitate construction of subclasses that provide more extensive monitoring facilities.
- Returns:
- the collection of threads
getExclusiveQueuedThreads
public final Collection<Thread> getExclusiveQueuedThreads()
Returns a collection containing threads that may be waiting to acquire in exclusive mode. This has the same properties as getQueuedThreads()
except that it only returns those threads waiting due to an exclusive acquire.
- Returns:
- the collection of threads
getSharedQueuedThreads
public final Collection<Thread> getSharedQueuedThreads()
Returns a collection containing threads that may be waiting to acquire in shared mode. This has the same properties as getQueuedThreads()
except that it only returns those threads waiting due to a shared acquire.
- Returns:
- the collection of threads
toString
public String toString()
Returns a string identifying this synchronizer, as well as its state. The state, in brackets, includes the String "State ="
followed by the current value of getState()
, and either "nonempty"
or "empty"
depending on whether the queue is empty.
- Overrides:
-
toString
in classObject
- Returns:
- a string identifying this synchronizer, as well as its state
owns
public final boolean owns(AbstractQueuedLongSynchronizer.ConditionObject condition)
Queries whether the given ConditionObject uses this synchronizer as its lock.
- Parameters:
-
condition
- the condition - Returns:
-
true
if owned - Throws:
-
NullPointerException
- if the condition is null
hasWaiters
public final boolean hasWaiters(AbstractQueuedLongSynchronizer.ConditionObject condition)
Queries whether any threads are waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, a true
return does not guarantee that a future signal
will awaken any threads. This method is designed primarily for use in monitoring of the system state.
- Parameters:
-
condition
- the condition - Returns:
-
true
if there are any waiting threads - Throws:
-
IllegalMonitorStateException
- if exclusive synchronization is not held -
IllegalArgumentException
- if the given condition is not associated with this synchronizer -
NullPointerException
- if the condition is null
getWaitQueueLength
public final int getWaitQueueLength(AbstractQueuedLongSynchronizer.ConditionObject condition)
Returns an estimate of the number of threads waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, the estimate serves only as an upper bound on the actual number of waiters. This method is designed for use in monitoring system state, not for synchronization control.
- Parameters:
-
condition
- the condition - Returns:
- the estimated number of waiting threads
- Throws:
-
IllegalMonitorStateException
- if exclusive synchronization is not held -
IllegalArgumentException
- if the given condition is not associated with this synchronizer -
NullPointerException
- if the condition is null
getWaitingThreads
public final Collection<Thread> getWaitingThreads(AbstractQueuedLongSynchronizer.ConditionObject condition)
Returns a collection containing those threads that may be waiting on the given condition associated with this synchronizer. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order.
- Parameters:
-
condition
- the condition - Returns:
- the collection of threads
- Throws:
-
IllegalMonitorStateException
- if exclusive synchronization is not held -
IllegalArgumentException
- if the given condition is not associated with this synchronizer -
NullPointerException
- if the condition is null